In recent years, for energy saving and heat insulation, fibrous heat-insulating materials, such as ceramic fibers, have been used for lining of furnace walls in various kiln equipment, such as heating furnaces and the like. The fibrous heat-insulating material has low thermal conductivity, is light-weight and has a small bulk specific gravity, and thus is excellent in thermal inertia, which advantageously enables a decrease in cooling and heating time in the furnace. For this reason, the fibrous heat-insulating material is used as a main lining material in a region where it is not in contact with a scale or melted metal in the heating furnace and the like.
Describing ceramic fiber (CF) as a typical fibrous heat-insulating material as an example, conventionally, when various furnaces are lined by using the ceramic fiber, a paper lining method of stacking a ceramic fiber blanket (CF blanket) formed by shaping the ceramic fiber into a blanket-like material on a support pin welded to a heated surface of a shell (furnace wall) has been adopted. However, the CF blanket have following problems: contraction in the thickness direction at elevated temperatures is large, a fitting such as the support pin is exposed in the furnace and thus, is susceptible to oxidation damage, and lining is relatively difficult since the CF blanket has a large area and a gap may be formed between layers thereof.
Thus, in recent years, a unit block obtained by folding a band-like CF blanket to have a predetermined length and stacking the layers of the CF blanket under pressure, or stacking a plurality of CF blanket pieces cut from the CF blanket to have a predetermined size, and forming the stacked layers of the CF blanket or CF blanket pieces into the shape of a block by sewing, bonding, use of built-in fitting or the like has been adopted. The unit block is used for lining in the state where its compressed shape is maintained by using a predetermined packing material and a binding band (see Non Patent Literatures 1 and 2).
For example, a CF block 31 as shown in FIGS. 7(a) and 7(b) is known as such CF block. The CF block 31 is manufactured by alternately folding a band-like CF blanket to have a predetermined length while making mountain folds and valley folds and stacking layers of the CF blanket under pressure to form a unit block 32 measuring about 300 mm×300 mm×300 mm, for example. The unit block 32 has a pair of pressed surfaces 32a that are pressed to finally from a block material used for lining, and a heated surface 32b heated in the lined state in the furnace. A block 32 is covered with a packing material 33 formed of a pair of packing members 33a, 33b, from the right and left pressed surfaces 32a to the heated surface 32b so as to protect each corner where the pressed surface 32a is in contact with the heated surface 32b, and is bound with two binding bands 34 via the packing material 33. The packing members 33a, 33b configuring the packing material 33 each consists of a pressed surface contact part 35 covering the pressed surface 32a of the block 32, a heated surface protection part 36 covering a part of the heated surface 32b for protection, and a bent part 37 formed between the pressed surface contact part 35 and the heated surface protection part 36. Reference numeral 38 in FIG. 7(b) shows a fitting for attaching the unit block 32 to the shell (furnace wall) at lining with a fibrous heat-insulating block 31. Reference numeral 39 in FIG. 7(a) is a paper tube guide pipe for operating the fitting 38 lining the fibrous heat-insulating block 31.
The CF blanket includes well-intertwined fibers and therefore, has a small heating contraction factor in its longitudinal direction and a relatively large heating contraction factor in its thickness direction. For this reason, as distinct from paper lining that uses a surface of the CF blanket as a heated surface and prevents heat transfer due to the thickness of the CF blanket, the lining using the CF block can orient its longitudinal direction to a main heat transfer direction, resulting in a high heat-insulating efficiency. Moreover, in the CF block, since the fitting (built-in fitting) for holding the shape of the CF block is inserted into the unit block, and the fitting such as a channel for attaching the unit block to the shell (see the reference numeral 38 in FIG. 7(b)) is exposed only on a cool surface of lining (surface on the opposite side to the heated surface), damage due to oxidation of the fitting can be suppressed, leading to a dramatic increase in life. In addition, since the CF block is provided with the guide pipe for bonding a support bolt welded to the shell to the unit block with a nut (see the reference numeral 39 in FIG. 7(a)), an attachment operation is easy. Further, since the CF block can be made to have easily-handled size, the workability of lining application can be greatly improved.
In lining using the CF block, the unit block formed by folding and stacking the layers of the CF blanket or stacking the CF blanket pieces of predetermined shape is used as one unit. In order to keep the shape of the unit block until lining and improve handleability until lining, the CF block is fixed to have predetermined size by placing a (paper) cardboard as the packing material on the pressed surface vertical to a stacking direction of the unit blanket and compressing them in the stacking direction and then, binding them with the binding band. In the case where the CF blanket is folded to form the CF block, the packing material to be used therefor protects fibers on the pressed surfaces 32a of the unit block 32, corners at boundaries between the pressed surfaces 32a and the heated surface 32b and the heated surface by extending the heated surface protection part 36 from the pressed surface contact part 35 covering the pressed surfaces 32a of the unit block 32 to the heated surface 32b as shown in FIGS. 7(a) and 7(b) such that mountain folds of the CF blanket are not damaged by fastening of the binding band. Generally, the heated surface protection part 36 is not in contact with the mounting folds of the CF blanket at its end, and is located at a position beyond the second mountain fold from the corners at the boundaries between the pressed surfaces 32a and the heated surface 32b, for the purpose of lower cost.
When the inner surface of the furnace wall is lined with the CF block, it is important to prevent the occurrence of a gap at a joint between the adjacent CF blocks. In the unit block of the CF block, the layers of the CF blanket are stacked and compressed between the pair of pressed surfaces under pressure. For this reason, the CF block has a little restoring force in the direction orthogonal to the CF blanket stacking direction, but has a restoring force in the stacking direction. Thus, some lining methods using the restoring force applied in the CF block stacking direction have been proposed.
For example, Patent Literatures 1 proposes a so-called checker method of arranging the cool surface (surface on the opposite side to the heated surface) on which the fitting such as the channel (see the member represented by the reference numeral 38 in FIG. 7(b)) is mounted toward an inner surface of the furnace wall, and alternatively lining the unit blocks while rotating by 90 degrees when viewed from the heated surface such that the CF blanket stacking directions of the adjacent unit blocks do not match each other. According to the checker method, by the restoring force in the CF blanket stacking direction, a pressing force is applied to each unit block from the direction orthogonal to the CF blanket stacking direction (direction in which the unit block itself exerts the restoring force), thereby suppressing the occurrence of a gap at the joint between the unit blocks. However, according to the checker method, when some unit blocks are displaced from each other, a gap at the joint between the adjacent unit blocks may occur. A triangular joint may be formed especially in a region where the four corners of the adjacent unit blocks gather, as it is difficult to concentrate the four unit block corners at one point. To supplement the joint, the joint is filled by inserting a fold into the gap at the joint, or filling a bulky ceramic fiber into the triangular joint.
In addition to the checker method, for example, Patent Literatures 2 proposes a so-called soldier method of arranging the plurality of unit blocks in a line such that their pressed surfaces are faced each other to form a unit block arrangement and inserting the CF blanket into a joint formed between rows of the unit block arrangement to fill the joint.
Patent Literature 3 describes a compression module that enables application of the CF blanket in its compressed state, and can prevent deformation or local destruction of the CF blanket to extend its durable lifetime. As shown in FIGS. 8(a) to 8(c), the compression module 41 in Patent Literatures 3 is manufactured by sandwiching a unit block formed of a plurality of stacked layers of the CF blanket 42 measuring 300 mm×300 mm between fish plates 44 made of a rigid material and compressing the layers, and then, binding the layers with a plurality of bands 45. The fish plates 44 in FIGS. 8(a) and 8(c) each has parts protruded from a heated surface 46 from the module 41, the fish plates in FIG. 8(a) each includes a handhold part 48 formed by bending a part of the protruded part toward the heated surface, and the fish plates in FIG. 8(c) each has a hole 49 in the protruded part as a handhold part. The fish plates in FIG. 8(b) each includes the handhold part 48 formed by inwardly bending a part of an end of the compression module 41 on the side of the heated surface 46.